On Thursday 23 March 2023 at 14:47 UTC, a login endpoint flood targeted a tax authority portal customer in the Nordics. The attack peaked at 17.2 million requests per second and lasted 79 minutes. Traffic originated from 4008 autonomous systems in 94 countries, predominantly a rented booter service.
| Vector | login endpoint flood |
| Peak | 17.2 million requests per second |
| Duration | 79 min |
| Time to mitigation | 0.539 s |
| Attack traffic reaching origin | 0.087% |
| Legitimate traffic challenged | 0.14% |
Timeline
The attack was preceded by a competitor’s product launch. Request rates on the targeted routes exceeded their hourly baseline by a factor of 464 within 14 seconds. The risk score of participating clients crossed the challenge threshold automatically and proof-of-work difficulty rose with origin load.
What the customer saw
The customer’s status page stayed green throughout; they learned about the attack from our notification.
Recommendations
- Review allow-listed partner ranges quarterly.
- Add a dedicated rate limit for the targeted route.
- Lower challenge thresholds on authentication endpoints during high-risk events.
We moved from a scrubbing provider to always-on last year; time to mitigation went from minutes to basically nothing.
Verified good bots and allow-listed partners bypass challenges entirely.
Interesting that most attacks are under ten minutes. Our experience is similar.